Various countries use different calendar systems. For example, although the Gregorian calendar, used primarily by Western countries, is generally accepted worldwide as a standard, its acceptance is sometimes reluctant. Many people would prefer dates to be presented in a more culturally sensitive form that is appropriate to a particular geographical location, such as where they live. Furthermore, even when different countries use the same calendar system today, a different calendar system may have been in use at some time in the past (e.g., when a country switched from the Julian calendar to the Gregorian calendar) or people in the same country may use different calendar systems for different purposes (e.g., for cultural events).
Tables in databases are often used to store date information. However, it may be desirable to access date information in a table using multiple formats (e.g., outputting date information in multiple formats), such as when a database is used internationally. Similarly, it may be desirable to perform operations on date information using multiple formats (e.g., comparing date information input by a user with date information stored in the table).